After a six-week delay to unravel a puzzling Range software glitch, United Launch Alliance's Atlas 5 rocket will try again Thursday afternoon to deploy a classified national security payload and batch of hitchhiking cubesats into space from California.

Liftoff is targeted for 2:39 p.m. local (5:39 p.m. EDT; 2139 GMT). The steady march of the payload orbit moved the launch about 10 hours earlier than the original blastoff time from the late-night try Aug. 2.

File image of an Atlas 5 rocket at VAFB. Credit: Pat Corkery/ULA

The mission will originate from Vandenberg Air Force Base's Space Launch Complex 3-East, a "classic pad" with a retractable service gantry and fixed umbilical tower. It stands in contrast to the Atlas 5's launch site at Cape Canaveral that assembles its rockets in an adjacent building and rolls the vehicles out to the spartan pad on a mobile platform.

This will be the fifth Atlas 5 to fly from the West Coast, each occurring successfully in the past four years with a trio of missions for the country's spy satellite agency and one with a U.S. military weather observatory.

Thursday's trip to space will deploy another cargo for the U.S. National Reconnaissance Office, the secretive government organization responsible for designing and operating the intelligence-gathering surveillance spacecraft for policy makers and military forces.

All details about the payload nestled inside the Atlas rocket's nose cone are kept classified. The agency will say only that the launch is known as NROL-36.

"Any NRO launch is critical to national security, delivering new intel capabilities out to the warfighters," said Lt. Col. Dan Gillen, commander of the 4th Space Launch Squadron that oversees Atlas 5 and Delta 4 rocket operations at Vandenberg. "Even though we are winding down some operations Afghanistan and Iraq, the need for intel is still growing."

Once the primary payload is delivered into its hush-hush orbital destination, the Centaur upper stage will maneuver to a different altitude where 11 miniature satellites built by universities, the military and a national lab will be ejected from 8 deployers all packed into one box-like container. That structure is attached to a bracket on the aft-end of the stage next to the RL10 engine where a helium bottle previously resided.

An illustration of an Atlas 5 rocket and the secondary payload attach location on the Centaur. Credit: NRO

Available performance on this mission made it suitable to fly the secondary cubesats and deliver them into a useful orbit.

Four are flying through NASA's Educational Launch of Nanosatellite program that works with schools to give students real-life experience in the space business. Institutions launching their scientifically-meaningful hardware on this rocket via ELANA are the University of California, University of Colorado at Boulder, California Polytechnic State University and Morehead State.

In addition, the NRO's Mission Support Directorate is enabling 7 satellites to fly from the Army Space and Missile Defense Command, the Aerospace Corp., the University of Southern California and the Lawrence Livermore National Laboratory.

Objectives of the various spacecraft range from testing future satellite technologies, probing space weather and observing the cosmic X-ray background.

The launch campaign began when the Atlas first stage and Centaur arrived at Vandenberg in April from ULA's production factory in Alabama.

This is the most-basic version of Atlas 5, known as the 401 configuration with a four-meter-diameter payload shroud, no strap-on solid-fuel motors and a single-engine Centaur.

Stacking of the vehicle occurred in May as the bronze first stage, equipped with its kerosene-fed RD-180 main engine, was brought to SLC 3, rotated vertical and set onto the pad. Then the cryogenic Centaur got hoisted into position.

Garrett Skrobot, a NASA manager on the ELANA project, said the cubesats were attached to the Centaur while the rocket was still horizontal in the hangar.

Payload hoisted into atop the Atlas 5 in July. Credit: ULA

The primary payload was readied for flight elsewhere on base and encapsulated in the nose cone before riding a special transport trailer to the pad to join up with its launcher on July 17.

The final launch readiness review was conducted Wednesday and gave approval for starting the countdown operations Thursday morning, with clocks picking up at 7 a.m. local. Retraction of the gantry to unveil the 19-story rocket occurs at 10 a.m. and fueling commences at 12:45 p.m.

Check out this rocket in a photo gallery posted from the Aug. 2 tower rollback.

The software issue during the Aug. 2 launch attempt hit Vandenberg's Mission Flight Control Center that computes radar, optical and telemetry data for safety specialists who track the rocket's path. The center has over 80 servers, eight operating systems and thousands of software processes, the Air Force says.

If a booster strays from its pre-set course, Range officials have the responsibility to destruct the rocket before it can threaten populated areas.

"Public safety is a huge part of our mission here at Vandenberg," said Col.
Hook, 30th Space Wing Operations Group commander. "Our team worked hard to
identify, test and restore the MFCC and we are excited to support a safe
and successful launch Sept. 13."

The logo for this NROL-36 mission. Credit: NRO

In an interview last week, Hook told a reporter from the local Santa Maria Times newspaper neighboring Vandenberg that the trouble was a "perfect storm" of timing that occurred as the countdown crossed 12 midnight. The team was performing a standard reinitialization of their computers to get into the final launch state while a background application in the control center was starting up at that exact time.

"It was during that process where we were reinitializing the computer that we recognized we had an issue because the screens did not come back up again," Hook said.

"This is related to the fact that this was spanning over the midnight hour. This application kicked off at midnight just as we were reinitializing the system. It was kind of a perfect storm of us reinitializing the system in addition to this background application that kicked off at midnight," Hook said. "If either one of those had occurred separately, it wouldn't have had an issue but it was the timing when they both occurred simultaneously that caused the problem."

Engineers have exhaustively tested out the system over the past several weeks at various hours of the day to gain confidence they understood the scenario that trigged the problem in the first place.

"Having sat through the past four weeks of analysis and testing, the team was extremely thorough in their analysis," Hook told the reporter. "We did testing at all hours of the day and night of both the simulator as well as the actual system. I am highly confident that we identified exactly what the cause was and that there is nothing else out that's similar that will cause this anomaly to occur again."

Payload requirements drive the launch time approximately 14 minutes earlier each passing day for the Atlas 5 to deliver the craft into the desired orbit. For the new Sept. 13 date, liftoff will occur in the mid-afternoon hours and avoid the countdown crossing midnight.

It will be the fourth of four launches for the NRO in 2012. A Delta 4 put a radar-imaging satellite into a retrograde orbit from Vandenberg in April, an Atlas 5 carried a geosynchronous data-relay bird in June from Cape Canaveral, followed by a Delta 4-Heavy with a clandestine cargo also flown from the Cape in late June.

About the author

Justin Ray has been editor of Spaceflight Now since its inception in November 1999. The online website, based at Cape Canaveral, has documented U.S. and international space news with a specialty of live launch coverage.

Prior to that, Justin worked for two years as an aerospace reporter at the Florida Today newspaper and its pioneering Space Online website. He began his career as an intern at Patrick Air Force Base's public affairs office in 1996 and wrote for the Missileer base newspaper.

The Ohio native has covered more than 115 Delta rocket launches, 85 Atlas flights, 65 space shuttle missions and construction of the International Space Station, plus scientific spacecraft such as the Mars rovers and Cassini.

He attended college at the University of Central Florida and now resides in Viera, Florida.

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